Fixed incorrect end position of comments in XmlFoldingStrategy.

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Folding/FoldingManager.cs

@@ -138,6 +138,8 @@ namespace ICSharpCode.AvalonEdit.Folding
 		{
 			if (startOffset >= endOffset)
 				throw new ArgumentException("startOffset must be less than endOffset");
+			if (startOffset < 0 || endOffset > document.TextLength)
+				throw new ArgumentException("Folding must be within document boundary");
 			FoldingSection fs = new FoldingSection(this, startOffset, endOffset);
 			foldings.Add(fs);
 			Redraw(fs);
@@ -254,6 +256,9 @@ namespace ICSharpCode.AvalonEdit.Folding
 					throw new ArgumentException("newFoldings must be sorted by start offset");
 				previousStartOffset = newFolding.StartOffset;
 				
+				int startOffset = newFolding.StartOffset.CoerceValue(0, document.TextLength);
+				int endOffset = newFolding.EndOffset.CoerceValue(0, document.TextLength);
+				
 				if (newFolding.StartOffset == newFolding.EndOffset)
 					continue; // ignore zero-length foldings
 				

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Folding/XmlFoldingStrategy.cs

@@ -110,7 +110,7 @@ namespace ICSharpCode.AvalonEdit.Folding
 					// into account the <!-- chars.
 					
 					int startOffset = GetOffset(document, reader) - 4;
-					int endOffset = startOffset + comment.Length + 3;
+					int endOffset = startOffset + comment.Length + 7;
 					
 					string foldText = String.Concat("<!--", comment.Substring(0, firstNewLine).TrimEnd('\r') , "-->");
 					foldMarkers.Add(new NewFolding(startOffset, endOffset) { Name = foldText } );

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Rendering/VisualLine.cs

@@ -151,13 +151,13 @@ namespace ICSharpCode.AvalonEdit.Rendering
 								offset += element.DocumentLength;
 								if (offset > currentLineEnd) {
 									DocumentLine newEndLine = document.GetLineByOffset(offset);
-									if (newEndLine == this.LastDocumentLine) {
+									currentLineEnd = newEndLine.Offset + newEndLine.Length;
+									this.LastDocumentLine = newEndLine;
+									if (currentLineEnd < offset) {
 										throw new InvalidOperationException(
 											"The VisualLineElementGenerator " + g.GetType().Name +
 											" produced an element which ends within the line delimiter");
 									}
-									currentLineEnd = newEndLine.Offset + newEndLine.Length;
-									this.LastDocumentLine = newEndLine;
 								}
 								break;
 							}
@@ -179,7 +179,7 @@ namespace ICSharpCode.AvalonEdit.Rendering
 				textOffset += element.DocumentLength;
 			}
 			VisualLength = visualOffset;
-			Debug.Assert(textOffset == LastDocumentLine.Offset + LastDocumentLine.Length - FirstDocumentLine.Offset);
+			Debug.Assert(textOffset == LastDocumentLine.EndOffset - FirstDocumentLine.Offset);
 		}
 		
 		internal void RunTransformers(ITextRunConstructionContext context, IVisualLineTransformer[] transformers)